1. Field of the Invention
The present invention relates to an apparatus for mobile communications, and more particularly to an apparatus and a method usable with a plurality of communications systems.
2. Description of the Related Art
At present, there are a variety of communications systems in use, differing with geographical area and application among other factors. For instance, there are the second generation personal handy phone system (PHS) and cordless systems, which are relatively inexpensive by virtue of the simplicity of network but do not warrant communication capability when in high speed transit. On the other hand, there are mobile telephone and cellular systems which do warrant communication capability in fast transit by virtue of steps taken against such disturbing factors as hand-over and fading though involving relatively high communication costs. Furthermore, there are pager systems allowing only reception while in transit.
Each of these many communications systems has its own hardware, such as PHS terminals and portable telephones.
However, with a view to enhancing the convenience of the users of such mobile wireless terminals, there are proposed portable wireless terminals which permit connection to a plurality of communication systems with a single unit.
It is considered preferable, in view of the cost of communication, for such a portable wireless terminal connectable to a plurality of communication systems, e.g. a cordless system and a cellular system, to preferentially access the cordless system. If access to the cordless system is given priority, even when the terminal is in a fast moving body, such as an automobile, access will be made to the cordless system which intrinsically does not warrant communication capability. In this case, when the bearer of the terminal has just got on the automobile, or the vehicle is waiting for a green light or running at a low enough speed not to affect communication, there will be no problem, but it is unrealistic to expect the vehicle to be always running so slowly or at halt. Therefore, if the bearer, while riding a vehicle, stands by or initiates a call via the cordless system, the conversation may be interrupted when the vehicle accelerates beyond a certain speed.